Methods involving a low resistance magnetic tunnel junction structure

ABSTRACT

The present disclosure describes methods for forming magnetic tunnel junction (MTJ) devices involving the use of diffusion components selected to alter the device properties. The magnetic tunnel junction structure is formed through diffusion components migrating from one layer of the MTJ structure to the tunneling barrier layer. Incorporation of the migrated components at the barrier layer adjusts the properties of the MTJ device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to magnetic storage systems andmore particularly to methods for forming low resistance magnetic tunneljunction devices.

2. Description of Related Art

Magnetic recording is a key segment of the information-processingindustry. While the basic principles are one hundred years old for earlytape devices, and over forty years old for magnetic hard disk drives, aninflux of technical innovations continues to extend the storage capacityand performance of magnetic recording products. For hard disk drives,the areal density or density of written data bits on the magnetic mediumhas increased by a factor of more than two million since the first diskdrive was used for data storage. Areal density continues to grow due toimprovements in magnet recording heads, media, drive electronics, andmechanics.

A magnetoresistive (MR) sensor changes resistance in the presence of amagnetic field. Recorded data can be read from a recorded magneticmedium, such as a magnetic disk, because the magnetic field from therecorded magnetic medium causes a change in the direction ofmagnetization in the read element, which causes a corresponding changein the sensor resistance.

Recently, magnetic tunnel junction sensor devices have been proposed fora variety of applications, including read heads for magnetic disks aswell as magnetoresistive random access memory. A magnetic tunneljunction (MTJ) is a type or magnetoresistive device made of at least twomagnetic film layers separated by an insulating barrier. The insulatingbarrier is thin enough to allow electrons to quantum mechanically tunnelthrough the barrier. Resistance of an MTJ is directly related to thetunneling probability that depends on the relative orientation of themagnetization vectors of the magnetic layers. Because the orientation ofthe magnetization vector depends on the applied field, the resistance ofa MTJ device varies in the presence of a magnetic field.

The MTJ device resistance limits the data access rate of a sensorincorporating an MTJ element. It is desirable to produce an MTJ sensorwith low resistance to increase the data access rate for magnetic readheads and MRAM elements.

SUMMARY OF THE INVENTION

To overcome the limitations in the prior art described above, and toovercome other limitations that will become apparent upon reading andunderstanding the present specification, the present invention disclosesmethods, devices and systems relating to a magnetic tunnel junctiondevice.

In accordance with one embodiment of the invention a method for forminga magnetic tunnel junction structure includes forming a first magneticlayer and a second magnetic layer. At least one of the first and thesecond magnetic layers includes diffusion components selected to adjustone or more properties of the magnetic tunnel junction device. Themethod further includes forming a barrier layer between the first andthe second magnetic layers. The barrier layer includes migrateddiffusion components from the at least one magnetic layer, wherein thediffusion components adjust the one or more properties.

In accordance with another embodiment of the invention a method offorming a magnetic tunnel junction device includes forming a magnetictunnel junction active region. The magnetic tunnel junction activeregion includes a first magnetic layer and a second magnetic layer. Atleast one of the first and the second magnetic layers includes diffusioncomponents selected to adjust one or more properties of the magnetictunnel junction device. The magnetic tunnel junction active regionfurther includes a barrier layer between the first and the secondmagnetic layers. The active region is annealed to enhance migration ofthe diffusion components from the first magnetic layer to the barrierlayer. The migrated diffusion components adjust the one or moreproperties of the magnetic tunnel junction device.

In accordance with yet another embodiment of the invention, a method forsensing a magnetic field comprises forming a magnetic tunnel junctiondevice. The magnetic tunnel junction device includes a first magneticlayer and a second magnetic layer. At least one of the first and thesecond magnetic layers includes diffusion components selected to adjustone or more properties of the tunnel junction device. The magnetictunnel junction device further includes a barrier layer between thefirst and the second magnetic layers. The method magnetic tunneljunction device is annealed to enhance migration of the diffusioncomponents from the first magnetic layer to the barrier layer. Themigrated diffusion components adjust the one or more properties of themagnetic tunnel junction device. The method of sensing a magnetic fieldfurther includes driving the magnetic tunnel junction device using anelectrical signal and detecting an electrical resistance based onmagnetic orientations of the first and the second magnetic layers.

These and various other advantages and features of novelty whichcharacterize the invention are pointed out with particularity in theclaims annexed hereto and form a part hereof. However, for a betterunderstanding of the invention, its advantages, and the objects obtainedby its use, reference should be made to the drawings which form afurther part hereof, and to accompanying descriptive matter, in whichthere are illustrated and described specific examples of an apparatus inaccordance with the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in which like reference numbers representcorresponding parts throughout:

FIG. 1 is a block diagram of a storage system in accordance withembodiments of the present invention;

FIG. 2 is a diagram of a magnetic disk storage system incorporating aMTJ sensor in accordance with embodiments of the present invention;

FIG. 3 illustrates a top view of components of a magnetic disk storagesystem in accordance with embodiments of the invention;

FIG. 4 illustrates an example of a magnetic disk read/write headincorporating a magnetic tunnel junction sensor in accordance withembodiments of the present invention

FIG. 5 illustrates an ABS view of a slider incorporating a MTJ sensor inaccordance with embodiments of the invention;

FIG. 6 illustrates a cross point architecture used in connection with amemory system in accordance with embodiments of the invention;

FIG. 7 illustrates the operation of a memory system incorporating MTJmemory elements in accordance with embodiments of the invention;

FIG. 8 illustrates the operation of a magnetic field sensor utilizing anMTJ device in accordance with embodiments of the invention;

FIGS. 9A and 9B illustrate the layered structure of an MTJ device beforeand after thermal processing, respectively, in accordance withembodiments of the invention; and

FIG. 10 is a flow graph of a method for forming a magnetic tunneljunction device in accordance with embodiments of the inventions.

DETAILED DESCRIPTION OF THE INVENTION

In the following description of the exemplary embodiment, reference ismade to the accompanying drawings, which form a part hereof, and inwhich is shown by way of illustration the specific embodiment in whichthe invention may be practiced. It is to be understood that otherembodiments may be utilized as structural changes may be made withoutdeparting from the scope of the present invention.

The present disclosure describes methods involving magnetic tunneljunction (MTJ) devices based on migration of junction enhancingdiffusion components from one layer of the MTJ structure to thetunneling barrier layer. According to various embodiments, a method forforming an MTJ device is described including forming a barrier layerincorporating migrated components from a magnetic layer. Incorporationof the migrated components into the barrier layer has been found todecrease the resistance of the MTJ device. For example, the migratedcomponents in the barrier layer decrease the bandgap of the barrierlayer, thus making it easier for carriers to tunnel from one magneticlayer to another. In addition, the migrated components reduce oxidationof the magnetic layer due to passivation provided by the migratedcomponents at the magnetic layer/barrier layer interface.

The MTJ device having an enhanced barrier layer may be formed bydepositing a first and a second magnetic layer, wherein at least one ofthe first and the second magnetic layer incorporates diffusioncomponents. The barrier layer is formed between the first and the secondmagnetic layers. The structure is annealed, facilitating the migrationof the diffusion components from the magnetic layer to the barrierlayer.

Any or all of the magnetic layers and barrier layer may have amulti-layered structure. In addition, one or more of the magnetic layersmay include one or more sub-layers that are non-magnetic. The magneticlayers, as referred to in this disclosure, generally refer to single ormulti-layered structures coupled through a tunneling barrier layer. Thediffusion components may homogeneous, comprising a single type ofelement, compound or other material, or may be heterogeneous, comprisingmultiple element, compound, or material types.

The MTJ device described in the present disclosure may be used inconnection with various technologies. In one example, the MTJ device maybe used as a component of a read head for reading data recorded on amagnetic disk. In another example, the MTJ device may be used as amemory element in a magnetic random access memory array.

FIG. 1 is a block diagram illustrating a magnetic data storage system100 that may incorporate an MTJ device in accordance with embodiments ofthe invention. The magnetic data storage system includes an actuator 120that controls the position of a transducer 110. The transducer 110writes and reads data on the magnetic media 130. The read/write signalsare passed to a data channel 140. A signal processor 150 controls theactuator 120 and processes the signals of the data channel 140. Inaddition, a media translator 160 is controlled by the signal processor150 to cause the magnetic media 130 to move relative to the transducer110. The present invention is not meant to be limited to a particulartype of storage system 100 or to the type of media 130 used in thestorage system 100.

FIG. 2 is a block diagram representing one example of a storage system200, e.g., a hard disk drive storage system, according to the presentinvention. The system 200 includes a spindle 222 that supports androtates at least on rotatable magnetic disk 220 when driven by motor224. Magnetic data is stored on the magnetic disk 220 in the form of anannular pattern of concentric data tracks (not shown).

At least one slider 226 is positioned on the disk 220, each slider 226supporting one or more magnetic read/write heads 228 where the heads 228incorporate a MTJ device of the present invention. As the disk(s) 220rotate, slider 226 is moved radially in and out over disk 220 so thatheads 228 may access different portions of the disk 220 where desireddata is recorded. Each slider 226 is attached to an actuator arm 232 bymeans of a suspension 234. The suspension 234 provides a slight springforce, which biases slider 226 against the disk 220. Each actuator arm232 is attached to an actuator 236. The actuator 236 may be a voice coilmotor (VCM). The VCM has a coil movable within a fixed magnetic field,the direction and speed of the coil movements being controlled by motorcurrent signals supplied by a control unit 240.

During operation of the disk drive 200, the rotation of the disk 220generates an air bearing between slider 226 and the disk 220, whichexerts an upward force or lift on the slider 226. The surface of theslider 226, which includes head 228 and faces the surface of disk 220 isreferred to as an air-bearing surface (ABS). The air bearing thuscounter-balances the slight spring force of suspension 234 and, duringnormal operation, supports the slider 226 off of, and slightly above,the disk 220 at a small, substantially constant spacing.

The various components of the disk drive 200 are controlled in operationby control signals generated by a control unit 240, such as accesscontrol signals and internal clock signals. Typically, control unit 240has logic control circuits, storage apparatus, and a microprocessor. Thecontrol unit 240 generates control signals to control various systemoperations such as drive motor control signals on line 242 and headposition and seek control signals on line 244. The control signals online 244 provide the desired current profiles to optimally move andposition the slider 226 to the desired data track on the disk 220. Readand write signals are communicated to and from read/write heads 228through recording channel 246.

The above description of a typical magnetic disk drive storage system200, and the accompanying illustration of FIG. 3 are for representationpurposes only. It should be apparent that disk storage systems maycontain a large number of disks and actuators, and that each actuatormay support a number of sliders. Many other variations of the basictypical magnetic disk drive storage system 200 may be used inconjunction with the present invention while keeping within the scopeand intention of the invention. However, those skilled in the art willrecognized that the present invention is not meant to be limited tomagnetic disk drive storage systems as illustrated in FIG. 2.

FIG. 3 is a top view 300 of a magnetic disk drive. The magnetic diskdrive 300 includes a spindle 332 that supports and rotates a magneticdisk 334. A combined read and write magnetic head 340 is mounted on aslider 342 that is supported by a suspension 344 and actuator arm 346.The present invention is not limited to a single unit, and a pluralityof disks, sliders and suspensions may be employed in a large capacitydirect access storage device (DASD). The suspension 344 and actuator arm346 position the slider 342 so that the magnetic head 340 is in atransducing relationship with a surface of the magnetic disk 334. Whenthe disk 334 is rotated by a motor, the slider is supported on a thincushion of air (air bearing) between the surface of the disk 334 and theair-bearing surface (ABS) (FIG. 4—448). The magnetic head 340 may thenbe employed for writing information to multiple circular tracks on thesurface of the disk 334, as well as for reading information therefrom.

FIG. 4 illustrates one example of a magnetic disk read/write headincorporating a magnetic tunnel junction sensor 400 according to thepresent invention. As shown in FIG. 4, first and second solderconnections 404 and 416 connect leads from the slider 442 to asuspension (FIG. 3—346). Third and fourth solder connections 418 and 406connect leads from a coil 440 in the magnetic head to the suspension(FIG. 3—346). However, one of ordinary skill in the art will realizethat the present invention is not meant to be limited the magneticsensor configuration shown in Figure, but that other MTJ sensorconfigurations may be used in the present invention.

FIG. 5 is a view of the slider 500 and magnetic head 510 from the airbearing surface. The slider has a center rail 520 that supports themagnetic head 510, and side rails 530 and 560. The support rails 520,530 and 560 extend from a cross rail 540. With respect to rotation of amagnetic disk, the cross rail 440 is positioned at a leading edge 550 ofslider 400 and the magnetic head 510 is positioned at a trailing edge570 of slider 500.

The above description of magnetic storage systems, shown in theaccompanying FIGS. 1-5, are for presentation purposes only and thepresent invention is not meant to be limited to the magnetic storagesystems illustrated therein. For example, magnetic storage systems maycontain a plurality of recording media, e.g., magnetic tape, and aplurality of actuators. Each actuator may support a number of sliders.In addition, instead of an air-bearing slider, the head carrier may beone that maintains the head in contact or near contact with the medium,such as in liquid bearing and other contact and near-contact recordingdevices.

FIG. 6 illustrates one embodiment of a magnetic memory device 600, e.g.,magnetic random access memory (MRAM). Memory elements of MRAM have atleast two magnetically stable states that can be written to and readfrom electronically. A memory device 600, such as MRAM, may beimplemented as a solid-state non-volatile magnetic storage device inwhich each bit of data is stored in a magnetoresistive element 610, suchas a magnetic tunnel transistor incorporating a magnetic tunneljunction. Magnetic tunnel transistors are described in commonly ownedU.S. Patent Application, identified by Ser. No. 10/428,474, and filed onMay 2, 2003, which is incorporated herein by reference in its entirety.

The non-volatility of MRAM devices provides an advantage overtraditional semiconductor dynamic RAM, because MRAM does not requiredata to be periodically refreshed. Further, MRAM devices provide theadvantages of low power consumption, high packaging density, and fastread and write access times.

Solid-state MRAM may use anisotropic magnetoresistance (AMR) films(i.e., a material that changes its resistance with an applied magneticfield) as the magnetoresistive element 610. The larger themagnetoresistive (MR) response (e.g., a response from a giantmagnetoresistance (GMR) film), the more commercially viable the MRAMbecomes. However, packaging of the MRAM using a GMR film is not asefficient as, for example, as the packaging of magnetic tunnel junctions(MTJs) of magnetic tunnel transistors (MTTs). The magnetic tunneljunctions of magnetic tunnel transistors provide high packing density byusing an implementation denoted cross-point architecture, described inmore detail below.

Cross point architecture presents one possible embodiment of an MRAMstructure comprising an array of parallel sense lines 620 and parallelword lines 630. At each junction of the parallel sense lines 620 andparallel word lines 630 is a magnetoresistive element 610. Themagnetoresistive element 610 may consist of two magnetic layers ofdifferent coercivity, one hard 640 and one soft 650. Magnetic fieldsgenerated by currents 660, 670 passing simultaneously through a senseline 620 and a word line 630 provides writing to an element 610 at theintersection of the two lines 620, 630. The detection of resistancechanges in a sense line 620 caused by a smaller measured current 670 inthe word line 630 provides a reading of the element 610.

More particularly, the direction of magnetization of the hard layer 640is used to represent the data bit. To write data, a magnetic field isapplied by passing a current 670 through a conductor line (word line630) adjacent to the element 610 such that the field is large enough tochange the magnetization of the hard layer 640. To read, a smallercurrent is passed, which can change the magnetization of the soft layer650 only. The resistance of the element depends on whether the hard 640and soft 650 layers are magnetized parallel or anti-parallel. Hence,changes in the resistance resulting from the reversal of the soft layer650 can be used to probe the magnetic state of the hard layer 640.

FIG. 7 illustrates the operation of a magnetic memory 700, e.g., MRAM,using MTJ devices as memory elements. The design in FIG. 7 uses amagnetic tunnel junction cell 710 consisting of two magnetic layers 720,725 separated by a thin insulating barrier layer 730. The magnetictunnel junction 710 is disposed at the intersection of sense lines 740and word lines 750. A first layer 720 polarizes the spins ofcurrent-carrying electrons, which cross the barrier 730 to a secondlayer 725 by quantum tunneling when both layers are aligned 760 toproduce, for example, a one bit (“1”) 770. When the magnetism of thesecond ferromagnetic layer is reversed 780, the tunneling is reduced anda zero bit (“0”) 790 is produced.

FIG. 8 illustrates an example embodiment of a magnetic sensor 800,suitable for use in a magnetic disk read head, implemented using an MTJdevice. In this example embodiment, a MTJ device comprises twoferromagnetic layers, 810, 830, and an insulating barrier layer 820disposed between the ferromagnetic layers 810, 830. Current through anMTJ results from electron tunneling through the barrier layer 820 fromone ferromagnetic layer 830 to the other ferromagnetic layer 810.Resistance of the MTJ sensor 800 is directly related to tunnelingprobability, which is dependent on the relative orientations of themagnetization vectors 860, 870 of the ferromagnetic layers 810, 830.

In one implementation, a first ferromagnetic layer 810, may be pinned,wherein the orientation of the magnetization vector 860 is fixed. Asecond ferromagnetic layer 830, may be a free magnetic layer, whereinthe orientation of the magnetization vector 870 is free to change basedon an applied magnetic field. When the MTJ sensor is moved into amagnetic field region, such as the magnetic field of a data bit recordedon a magnetic disk, the orientation of the magnetization vector 870 ofthe free layer aligns according to the applied field.

The dependence of tunneling on the relative orientation of themagnetization vectors 860, 870 arises from the asymmetry in the electrondensity of states of the majority/minority carrier energy bands in theferromagnetic material. When the magnetization vectors 860, 870 areparallel, the number of occupied energy states in one magnetic layer andavailable energy states in the other magnetic layer is at a maximum.This situation creates an increased tunneling probability, and tunnelingresistance is decreased. When the magnetization vectors 860, 870 areanti-parallel, there is a mismatch between the number of occupied statesin one magnetic layer 830 and the available energy states in the othermagnetic layer 810. Anti-parallel alignment of the magnetization vectors860, 870 causes tunneling to decrease, which leads to an increase in theresistance of the MTJ. The change in the resistance of the MTJ may bedetected by driving the junction with a small sense current 840 anddetecting the change in the magnetoresistance 850 of the MTJ as the MTJis moved through the magnetic field.

The resistance of the MTJ devices must be low, e.g., less than 1 Σmicrometer square and maintain an acceptable magnetoresistive response.The use of low bandgap materials to form the barrier layer of 830 of MTJdevices decreases the resistance of the MTJ device. Typically, thebarrier layer 830 may be formed using naturally oxidized AlO_(x) Barrierlayers comprised of lower bandgap materials, e.g., ZrAlO_(x), HfAlO_(x),provide decreased resistance while maintaining reasonable MR response.

In accordance with various embodiments of the invention, low bandgap,low resistance MTJ devices may be formed through controlled migration ofdiffusion components from a magnetic layer towards or into the barrierlayer. The diffusion components, e.g., Hf, Zr, migrate toward or intothe barrier layer, e.g., comprised of AlO_(x), due to the affinity ofthe diffusion components to oxygen. Incorporation of certain diffusioncomponents from the magnetic layer into the barrier layer has been foundto decrease the resistance of the MTJ device and/or lower the bandgap ofthe barrier layer. The migrated components may also passivate thematerial at the pinned magnetic layer/barrier layer interface, thusreducing oxidation of the pinned magnetic layer and increasing the MRresponse of the MTJ device.

An MTJ device having an enhanced barrier layer may be formed bydepositing a first and a second magnetic layer, wherein at least one ofthe first and the second magnetic layer incorporates a diffusioncomponent. The diffusion component is an element, compound, or othercomplex that migrates from a layer, e.g., the magnetic layer, of the MTJto the barrier layer. The diffusion component may be used to decreasethe resistance, lower the bandgap, passivate the layers of the magnetictunnel junction, and/or otherwise enhance the properties of the MTJdevice. The barrier layer is formed between the first and the secondmagnetic layers. Diffusion of the diffusion component may be facilitatedthrough annealing or other thermal processing of the MTJ structureduring manufacture.

FIG. 9A illustrates one example of the layered structure of an MTJdevice prior to thermal processing in accordance with embodiments of theinvention. A first magnetic layer 916 of the MTJ device 900 may comprisea multi-layered structure that may be anti-ferromagnetically (AFM)pinned or self-pinned. An anti-ferromagnetically pinned magnetic tunneljunction comprises a structure having at least one ferromagnetic (FM)layer that is pinned by a nearby anti-ferromagnetic (AFM) layer. Ananti-ferromagnetically pinned structure comprises at least oneferromagnetic (FM) layer adjacent to a thin non-ferromagnetic layer. Theferromagnetic layer is called the pinned layer because it ismagnetically pinned or oriented in a fixed and unchanging direction by athick adjacent AFM layer, commonly referred to as the pinning layer. Thepinning layer pins the magnetic orientation of the pinned layer throughanti-ferromagnetic exchange coupling.

In a self-pinned device, the magnetic moment of the pinned layer may bepinned in the fabrication process; i.e., the magnetic moment is set bythe specific thickness and composition of the film. The self-pinnedlayer may be formed of a single layer of a single material or may be acomposite layer structure of multiple materials. It is noteworthy that aself-pinned MTJ requires no additional external layers applied adjacentthereto to maintain a desired magnetic orientation.

The active layers of the MTJ device may be fabricated on a substrate 905comprised of any suitable composition including semiconductor material,glass, or a ceramic material such as alumina (Al₂O₃). The MTJ device 900may be fabricated in any acceptable system to sequentially deposit themultilayer structure on a substrate 905 as shown in FIG. 9A.

A seed layer 918 may be deposited on the substrate 905 to modify thecrystallographic texture or grain size of the subsequent layers. Theseed layer 918 may be multiple layers or a single layer, e.g., a singlePtMn layer adjacent to substrate 905.

In one embodiment of the present invention, a first magnetic layer 919may comprise a self-pinned structure. The first magnetic layer mayinclude, for example, at least two ferromagnetic films 915, 917separated by a thin anti-ferromagnetic coupling film 916. In thisstructure, a thick adjacent anti-ferromagnetic layer used for pinningthe pinned layer can be eliminated. The two ferromagnetic films 915, 917comprising the laminated pinned layer are anti-ferromagnetically coupledto one another by means of the appropriate type and thickness of theanti-ferromagnetic coupling film 916 so that the magnetizations of thetwo ferromagnetic films 915, 917 are oriented anti-parallel to oneanother.

For example, the self-pinned multi layer structure 919 may include acomposite laminate structure having a first layer 917 comprised of CoFe,an inner layer 916 comprised of Ru, and a second layer 915 comprised ofan alloy of CoFe and incorporating diffusion components of a suitablediffusion element X, e.g., CoFeHf or CoFeZr. The composite laminatestructure achieves high pinning strength due to the use of the positivemagnetostriction of the CoFe material. However, the invention is notlimited to these materials and other materials are possible for use inplace of the CoFe and Ru materials to form the first magnetic layer 919.

High pinning strength is required to maintain a first magnetic vectororientation (FIG. 8, 860) allowing the self-pinned layer to besubstantially constant while being exposed to non-magnetizing effects.Such increased pinning strengths are effective to, among other features,increase the dynamic range of the magnetoresistive tunneling effect,i.e., the magnitude of the change in resistivity of MTJ device 900.Also, the self-pinning field of pinned layer 919 should be greater thanany demagnetizing fields at an operating temperature of the MTJ device900 to insure that the magnetization direction (FIG. 8, 860) ofself-pinned structure 916 remains substantially fixed during theapplication of the external signal fields.

The first magnetic layer 919 comprises the alloy of CoFe andincorporates diffusion components selected to adjust one or moreproperties of the device, e.g., series resistance and/or barrier layerbandgap. The alloy of CoFe is denoted herein as CoFeX, where X is anyappropriate element, compound or other material, including, e.g., Hf orZr. CoFeX may be deposited by any suitable method as an amorphous alloyproviding a very smooth layer for the growth of the very thin barrierlayer to avoid pinholes and other defects that may increase theresistance of the barrier layer 914.

A barrier layer 914 may be formed adjacent to the first magnetic layer919. The barrier layer 915 may be comprised, for example, of AlOx havinga thickness in a range of about 3 to about 6 Δ. A second magnetic layer912 may be formed adjacent to the barrier layer 914. The second magneticlayer formed of a ferromagnetic material, such as CoFe, or NiFe. Thesecond magnetic layer may be a layered structure, as illustrated inFIGS. 9A and 9B, of ferromagnetic materials. A cap layer 910 may beformed adjacent the second magnetic layer 912.

FIG. 9B shows the structure of the MTJ device following thermalprocessing, e.g., annealing at a temperature less than about 300 C.(degree centigrade). As illustrated in FIG. 9B, a portion of thediffusion components, e.g., Hf and/or Zr, migrate from the CoFeX alloylayer 925 of the first magnetic layer 929 to the barrier layer 924. Thediffusion elements may be incorporated into the barrier layer 924forming a barrier layer comprising XAlO_(x). As previously discussed,incorporation of the migrated diffusion components into the barrierlayer adjusts the properties of the MTJ device. For example,incorporation of the diffusion components into the barrier layer 924 maylower the bandgap of the barrier layer 924 and/or decrease theresistance of the MTJ device 900. Further, the diffusion components mayact to passivate the pinned layer 925/barrier layer 924 interface, thuspreventing oxidation of the pinned layer 925 and increasing the dR/Rresponse.

FIG. 10 is a flow graph illustrating a method of manufacturing a MTJdevice according to example embodiments of the invention. A firstmagnetic layer is formed 1010 incorporating a diffusion component. Abarrier layer is formed 1020 adjacent the first magnetic layer. A secondmagnetic layer 1030 is formed adjacent the barrier layer. The MTJstructure is annealed to facilitate migration of the diffusioncomponents from the first magnetic layer into the barrier layer 1040.

The foregoing description of the exemplary embodiment of the inventionhas been presented for the purposes of illustration and description. Itis not intended to be exhaustive or to limit the invention to theprecise form disclosed. Many modifications and variations are possiblein light of the above teaching. It is intended that the scope of theinvention be limited not with this detailed description, but rather bythe claims appended hereto.

What is claimed is:
 1. A method of forming a magnetic tunnel junctiondevice, comprising: forming a first magnetic layer and a second magneticlayer, at least one of the first and the second magnetic layersincluding diffusion components selected to adjust one or more propertiesof the magnetic tunnel junction device; and forming a barrier layerbetween the first and the second magnetic layers, the barrier layercomprising migrated diffusion components from the at least one magneticlayer, wherein the diffusion components adjust the one or moreproperties.
 2. The method of claim 1, wherein the diffusion componentsare selected to adjust a series resistance of the magnetic tunneljunction device.
 3. The method of claim 1, wherein the diffusioncomponents are selected to decrease a bandgap of the barrier layer. 4.The method of claim 1, wherein: forming the first magnetic layercomprises forming a pinned magnetic layer; and forming the secondmagnetic layer comprises forming a free magnetic layer.
 5. The method ofclaim 1, wherein one or more of the first and the second magnetic layerscomprises a multi-layer structure.
 6. The method of claim 1, wherein oneor more of the first and the second magnetic layers comprises an alloyof CoFe.
 7. The method of claim 6, wherein the alloy of CoFe comprisesCoFeHf.
 8. The method of claim 7, wherein the CoFeHf comprises about 5to about 10 atomic percent Hf.
 9. The method of claim 6, wherein thealloy of CoFe comprises CoFeZr.
 10. The method of claim 9, wherein theCoFeZr comprises about 5 to about 10 atomic percent Zr.
 11. The methodof claim 1, wherein the diffusion components comprises Hf.
 12. Themethod of claim 1, wherein the diffusion components comprises Zr. 13.The method of claim 1, wherein forming the first and the second magneticlayers comprises forming at least one amorphous layer.
 14. The method ofclaim 1, wherein forming the barrier layer comprises forming a layercomprising a compound of AlOx having a thickness of about 3 Δ to about 6Δ.
 15. The method of claim 1, wherein the forming the barrier layercomprises forming a barrier layer comprising AlHfOx.
 16. The method ofclaim 1, wherein forming the barrier layer comprises forming a barrierlayer comprising AlZrOx.
 17. A method of forming a magnetic tunneljunction device, comprising: forming a magnetic tunnel junction activeregion, comprising: a first magnetic layer and a second magnetic layer,at least one of the first and the second magnetic layers includingdiffusion components selected to adjust one or more properties of themagnetic tunnel junction device; and a barrier layer between the firstand the second magnetic layers; and annealing the active region toenhance migration of the diffusion components from the first magneticlayer to the barrier layer, wherein the migrated diffusion componentsadjust the one or more properties.
 18. The method of claim 17, whereinthe at least one layer comprises an alloy of CoFe.
 19. The method ofclaim 17, wherein the at least one layer comprises CoFeHf.
 20. Themethod of claim 19, wherein the CoFeHf comprises about 5 to about 10atomic percent Hf.
 21. The method of claim 17, wherein the at least onelayer comprises CoFeZr.
 22. The method of claim 21, wherein the CoFeZrcomprises about 5 to about 10 atomic percent Zr.
 23. The method of claim17, wherein the diffusion components comprise Hf.
 24. The method ofclaim 17, wherein the diffusion components comprise Zr.
 25. The methodof claim 17, wherein the barrier layer has a thickness of about 3 Δ toabout 6 Δ.
 26. The method of claim 17, wherein annealing the activeregion comprises annealing the active region at a temperature of lessthan about 300 C.
 27. The method of claim 17, wherein the diffusioncomponents are selected to decrease a series resistance of the activeregion.
 28. The method of claim 17, wherein annealing the diffusioncomponents are selected to decrease a band gap of the barrier layer. 29.The method of claim 17, wherein annealing the active region to enhancemigration of the diffusion components from the first magnetic layer tothe barrier layer comprises forming AlHfOx in the barrier layer.
 30. Themethod of claim 17, wherein annealing the active region to enhancemigration of the diffusion components from the first magnetic layer tothe barrier layer comprises forming AlZrOx in the barrier layer.
 31. Amethod for sensing a magnetic field, comprising: forming a magnetictunnel junction device having an active region, comprising: a firstmagnetic layer and a second magnetic layer, at least one of the firstand the second magnetic layers including diffusion components selectedto adjust one or more properties of the magnetic tunnel junction device;and a barrier layer between the first and the second magnetic layers;and annealing the active region to enhance migration of the diffusioncomponents from the first magnetic layer to the barrier layer, themigrated diffusion components adjusting the one or more properties;driving the magnetic tunnel junction device using an electrical signal;and detecting an electrical resistance based on magnetic orientations ofthe first and the second magnetic layers.
 32. The method of claim 31,wherein the at least one layer comprises CoFeHf.
 33. The method of claim31, wherein the at least one layer comprises CoFeZr.
 34. The method ofclaim 31, wherein the diffusion components comprise Hf.
 35. The methodof claim 31, wherein the diffusion components comprise Zr.
 36. Themethod of claim 31, wherein annealing the active region comprisesannealing the active region at a temperature of about 300 C.
 37. Themethod of claim 31, wherein the diffusion components are selected toreduce a series resistance of the active region.
 38. The method of claim31, wherein the diffusion components are selected to decrease a bandgapof the barrier layer.
 39. The method of claim 31, wherein annealing theactive region to enhance migration of the diffusion components from thefirst magnetic layer to the barrier layer comprises forming AlHfOx inthe barrier layer.
 40. The method of claim 31, wherein annealing theactive region to enhance migration of the diffusion components from thefirst magnetic layer to the barrier layer comprises forming AlZrOx inthe barrier layer.